Microwave circuit housing

ABSTRACT

A two-piece housing composed of a lower member presenting a support surface for supporting at least one microstrip substrate and in which are formed a plurality of cavities disposed along its edges, the member also having an upstanding rim surrounding the support surface and provided with a plurality of recesses, each recess being disposed adjacent a respective cavity. The other member of the housing is a cover member having a top surface arranged to be disposed opposite the support surface of the bottom member to define a chamber in which a microstrip substrate is disposed, and a rim portion arranged to rest on the upstanding rim of the bottom member. The cover member rim portion is provided with recesses arranged to cooperate with the recesses in the bottom member rim portion to define openings for the passage of connectors. One such housing could be employed by itself as a single microwave circuit package or it could be employed in combination with similar housings as one module of a more complex circuit.

United States Patent MICROWAVE CIRCUIT HOUSING 11 Claims, 15 Drawing Figs.

U.S. Cl. 317/101, 29/592, 174/59 Int. Cl. 1102b l/04 Field of Search 317/99,

101, 101 (CB), 101(A,B,C), 101 (CX,Dl-I); 339/119, 120, 121,125, 14, 17, 147; 174/685 References Cited UNITED STATES PATENTS 2,934,748 4/1960 Steimen... 317/99X 3,428,954 2/ 1969 David 174/68.5X

Primary Examiner-Laramie E. Askin Assistant Examiner-D. A. Tone Attorney-Spencer and Kaye ABSTRACT: A two-piece housing composed of a lower member presenting a support surface for supporting at least one microstrip substrate and in which are formed a plurality of cavities disposed along its edges, the member also having an upstanding rim surrounding the support surface and provided with a plurality of recesses, each recess being disposed adjacent a respective cavity. The other member of the housing is a cover member having a top surface arranged to be disposed opposite the support surface of the bottom member to define a chamber in which a microstrip substrate is disposed, and a rim portion arranged to rest on the upstanding rim of the bottom member. The cover member rim portion is provided with recesses arranged to cooperate with the recesses in the bottom member rim portion to define openings for the passage of connectors. One such housing could be employed by itself as a single microwave circuit package or it could be employed in combination with similar housings as one module of a more complex circuit.

PATENTEB FEBZ 3 I97:

SHEET 1 OF 2 mm l b 3fl5v 4 H n A a K31 j g V o? m w N. hm m :3 wm @E g v mm INVENTOR afield H055? ATTORNEYS PATENTEU FEBZ 31am 3; 566; 191

sum 2 or z mvsmon Ronald Holst BY/4mw/ W ATTORNEY 5 MECROWAVE CIRCUIT HOUSING BACKGROUND OF THE INVENTION The present invention relates to a housing for microwave circuits, and particularly to a housing which can be readily linked with other housings in a modular manner to create a complete RF system or subsystem.

In recent years, the use of microstrip techniques in the construction of RF circuits has increased considerably. Microstrip circuits are highly desirable for many RF applications because of their small size and dependability and because they lend themselves to completely automated fabrication procedures.

However, up to the present there have been limitations on the uses which could be made of such circuits. Because of the difficulty generally encountered in connecting together individual microstrip circuit units without degrading their high frequency performance, it has usually be considered necessary to fabricate complete microwave circuits as one-piece units. As a result, use of the microstrip technique has been limited in practice to those situations where cost is a minor factor or where a particular circuit is to bemanufactured in large quantities.

However, there is presently no practically feasible technique for economically constructing integrated microstrip RF circuits from a plurality of basic prepackaged units.

SUMMARY or THE INVENTION It is a primary object of the present invention to overcome these drawbacks and difficulties.

Another object of the invention is to package microstrip circuit elements for use as modules in integrated microstrip circuits.

A further object of the invention is to facilitate the connection together of a plurality of such modules to form any desired integrated RF circuit.

A still further object of the invention is to provide a novel microstrip element housing which can be used alone as a microstrip circuit element or which can be readily combined with similar housings to form an integrated microstrip circuit.

These and other objects according to the invention are achieved by the provision of a novel housing for at least one microstrip RF circuit element formed on a substrate. The housing according to the invention is composed essentially of polygonal bottom and cover portions spaced from one another to define a chamber in which such element is to be disposed, and a rim extending between the portions, along the edges thereof, and delimiting the lateral edges of the chamber. The bottom portion is provided with cavities extending from the surface thereof which bounds the chamber, the cavities being disposed along the edges of the bottom portion for holding connecting elements. The rim is provided with passages through which the connecting elements can extend out of the housing, there being one such passage adjacent each cavity.

The objects according to the invention are further achieved by the provision of a flat carrier for at least one microstrip RF circuit element formed on a substrate, the carrier including a polygonal carrier plate having the lower half of each of its edges cut away and the upper half of each of its edges provided with at least one slot for receiving a circuit connecting element which, when in place, extends below the upper half of such edge. The flat carrier further includes holding means disposed in the cutaway portion of each edge of the plate for bearing against such connecting element, and attachment means extending between each strip and its associated edge of the plate for attaching the strip to the plate and for clamping the connecting element between the strip and its associated plate edge.

DESCRIPTION OF THE DRAWINGS FIG. 1a is a top plan view of the bottom member of a preferred embodiment of a housing according to the invention;

FIG. lb is a cross-sectional, elevational view taken along the line lb-lb of FIG. ia;

FIG. 10 is an elevational view of the member of FIG. la;

FIG. 2a is a bottom plan view of the top member of a preferred embodiment of the housing according to the invention;

FIG. 2b is a cross-sectional, elevational view taken along the line 2b-2b of FIG. 2a;

FIG. 3a is a side view of one connector which can be used in embodiments of the invention;

FIG. 3b is an end view of the'connector of FIG. 30;

FIG. 4a is a side view of another connector which can be used in embodiments of the invention;

FIG. 4b is a cross-sectional view taken along the line 4b-4b of FIG. 40;

FIG. 5a is an end view of an insulating plug which can be used in embodiments of the invention;

FIG. 5b is a side view of the plug of FIG. 5a;

FIG. 6 is a cross-sectional, elevational view, taken along the lines 6-6 of FIGS. la and 20, showing the preferred embodiment of the housing according to the invention in its assembled condition;

FIG. 7 is a plan view of another embodiment of the invention;

FIG. 8 is an elevational view of a portion of the device of FIG. 7;

FIG. 9 is a cross-sectional view along the plane 9-9 of FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. la, lb and 1c, there is shown the bottom member 1 of a housing according to the invention. This member is preferably made in one piece of a material which is suitably rigid and easily machined, one example of such a material being aluminum. The member is preferably plated, for example with gold, to serve as a conductive ground plane portion for the microstrip circuit.

The bottom member is composed of a support portion 3 which is provided for supporting one or several microstrip circuit elements mounted on substrates, such support preferably being through the intermediary of a mounting arrangement such as a combination of a male/female standoff and a cone spring washer. This permits the substrate on which the microstrip element is formed to be preloaded with respect to the ground plane defined by the housing, such preloading being highly advantageous because it allows for thermal expansion of the various components. The bottom member is further composed of an upstanding rim portion 5 completely surrounding the support portion 3 and extending above the support surface of the support portion.

FIG. 1b shows one such standoff 6 and its associated cone spring washer 8. The standoff 6 is screwed into a threaded opening 13 in bottom member I and is arranged to urge cone spring washer 8 against the upper surface of a substrate (not shown) resting on support portion 3. Standoff 6 has a threaded bore 6 for receiving a holddown screw which fastens a top member to a bottom member 1. Such a top member will be described in detail below with reference to FIGS. 20 and 2b.

The support portion 3 is provided with a plurality of downwardly extending cavities 9, which are best shown in FIG. lb. Each cavity is disposed adjacent the upstanding rim portion 5 and is provided for holding a connection element, as will be described in greater detail below. The support portion 3 is further provided with four threaded recesses I5, each disposed at the midpoint of a respective edge of the support portion, for receiving holddown screws which connect the housing top member, shown in FIGS. 20 and 2b, to the bottom member. The bottom portion-further includes five threaded holes 13, one at each corner and one at the center.

Male/female standoffs may be Screwed into various ones of the threaded openings 13 and recesses 15 to provide support elements for the microstrip substrates. When standoffs are screwed into the recesses 15, the holddown screws inserted through the openings 35 in the top member 21 are screwed directly into the standoffs for fastening the top member to the bottom member. I

The upstanding rim portion is provided with indentations around each of the holes 11 and 13 and is further provided with cutouts 7, preferably of semicircular-shape, via which connectors extend out of the housing, each cutout 7 being disposed adjacent a respective cavity 9.

The housing is completed by atop member 21, shown in FIGS. 2a and 2b. The top member includes a cover portion 23 and a downwardly projecting rim portion 25. The cover portion 23 is provided with countersunk'bores 35 for the passage of the holddown screws which are to secure the top member 21 to the bottom member LThe rim portion 25 is provided with indentations 31 around each bore 35, and at the corners of the top member and is also provided with cutouts 27, also preferably of semicircular shape, positioned to cooperate with the cutouts 7 to define openings for the connectors which are to be associated with the circuit provided in the housing. The top member 21 may be made of the same material as the bottom member 1, and it may be similarly plated.

When the housing is assembled, the cover portion 23 is spaced above the bottom portion 3 so that a chamber for the microstrip circuit elements is, defined between these two portions. The housing may hold a single substrate whose dimensions substantially conform with the'area enclosed by the rims 5 and 25, or it may hold several, e.g., four, substrates whose total area is equal to the area enclosed by the rims. Altematively, the housing may hold any combination of substrates through the use of the overlay technique. The microstrip circuit formed on each substrate is constructed so that its exter-' nal connection points are aligned with the connectors disposed in the regions defined by cavities 9 and cutouts 7 and 27.

One type of connector which may be employed in embodiments of the invention is shown in FIGS. 30 and 3b to be constituted by a coaxial RF connector having a shank portion 37 carrying screw threads 38 for connection to a mating connector. The shank portion 37 is integral with a flange portion 36. A center conductor 39 extends'through the connector and is supported with respect thereto by an insulating sleeve 40 which is coextensive with the length of the connector.

This connector is mounted in the housing by the insertion of the bottom half of its flange 36 into one of the cavities 9 in such a manner that the projecting portion of the center conductor 39 extends into the housing for connection to the microstrip circuit element provided therein, while the shank portion 37 extends through the passage formed by the corresponding cutouts 7 and 27. The flange 36 is dimensioned to fit securely in the cavity 9 and to be held securely between the bottom of the cavity and the cover portion of top member 21. After the housing has been assembled, the connector will be prevented from undergoing any axial movement with respect to the housing. y t

It should be particularly noted that the connector shown in FIGS. 3a and 3b can be securely retained in the housing without the use of any screws or other attachment elements. The secure mounting of the connector flange 36 assures that a strong mechanical connection as well as a good electrical connection will be formed between this flange and the housing. This connector is employed to provide an external connection for a circuit housed in one or several of the housings according to the invention.

FIGS. 4a and 4b illustrate one embodiment of a connector for directly connecting together two housings according to the invention. The connector includes two flanges 41 and 42 con- .the flanges 41 and 42 in their respective cavities 9 will cause the, two housings to be held firmly against one another with their rims in abutting relationship. At the same time, the connector will provide a good electrical connection between the bottom members of the two abutting housings. The lower inner edges of each flange are provided with chambers 44 to facilitate their insertion in the cavities 9.

FIGS. 54 and 5b show one further element which may be advantageously employed in embodiments of the invention for sealing any openings 7, 27 which are not be provided with connections. This element constitutes a plug having a flange portion 51 and a stern portion 52, the flange 51 being insertable in a cavity 9 and the stem 52 being shaped to close the corresponding opening 7, 27. This plug, which may be made of any suitable insulating material such as a thermosetting plastic, serves to seal ofi any housing opening which is not in use.

Turning now to FIG. 6, there is shown an assembled housing according to the invention composed of a bottom member 1 and a top member 21 resting on, and fastened to,the bottom member 1. One opening, or port, of the housing is provided with a coaxial connector of the type shown in FIGS. 3a and 3b. The end of the center conductor39 which extends into the housing is positioned to make electrical contact with an extremity of the microstrip circuit disposed in the housing and carried by substrate 22. Substrate 22 is held down by standoffs 6, which may be provided with washers 8.

The housing is also provided with a coupling connector of the type shown in FIGS. 4a and 4b which serves to create a rigid mechanical connection with an adjacent housing composed of a bottom member la and a top member 21a. The ground planes defined by the two housings are conductively connected together by the connector, while an insulated center conductor can be inserted in the opening 43 of the connector to connect together the. microstrip circuits disposed in the two adjacent housings.

It may thus be seen that the present invention provides a housing connector combination which permits the ready connection together of prepackaged basic microstrip modular units to form any desired microstrip RF circuit. Housings according to the invention are structurally simple, being made of a small number of parts, and are easy to assembly, primarily sincethe various connectors and plugs employed with such housings only need to be inserted in their associated cavities in the housing bottom member and will automatically become securely connected, both mechanically and electrically, to the housing when the top memberis positioned on, and fastened to, the bottom member.

In practical embodiments of housings according to the invention, each housing is preferably dimensioned to receive a single 1 inch square microstrip substrate or four xiinch square microstrip substrates which are electrically connected together before the housing is assembled.

FIGS. 7, 8 and 9 show another embodiment of the invention which is in the form of a unitary flat carrier plate 61 for receiving a plurality of microstrip circuit substrates, or wafers, 22. Such a flat carrier is well adapted for use in the breadboard" construction of prototype microstrip circuits and can be employed in place of the shieldedihousing illustrated in FIGS. 1 to 6, particularly when RFl shielding and intercircuit isolation are not of great concern.

FIG. 7 shows the flat carrier plate 61 on which are disposed two such substrates 22. The flat carrier plate 61 is provided with a regular array of threaded openings 13 for receiving standoffs 6 which serve to hold down the various substrates.

The plate 61 is dimensioned, and the openings 65'distributed, for permitting standardized substrates to be mounted so as to abut against one another. lt is then a simple matter for connections to be made between the corresponding conductors at the edges of two adjacent substrates.

Along the edge of the flat carrier are disposed a series of trapezoidal slots 63 for receiving the various types of connectors illustrated in FIGS. 3-5. The lower half of each edge of the plate is cut away to receive a holding strip 70which is attached to the plate 61 by means of flathead machine screws 71 and which serves to mechanically grip the connectors inserted in the slots disposed along the corresponding edge of the plate.

FIG. 8 shows the arrangement between the strips 70 along two adjoining edges of the plate and the relation between screws 71 and slots 63. The dotted line in FIG. 8 illustrates the cutaway portion of the plate 61, which, in this view, is hidden by the strips 70.

Turning now to FIG. 9, which is'to an enlarged scale, there is shown a typical connector, which is of the type shown in FlGS. 3a and 3b, inserted in a slot 63 so that its flange portion 36 is disposed between the edge of the plate and a strip 70. Once all of the connectors required for one edge of the plate have been inserted in their respective slots, a strip 70 is positioned and clamped against connector flange portion 36 by two or more screws 71.v FIG. 9 also shows one substrate 22 mounted in position to have one of its conductive elements connected to the center conductor 39 of the connector. The substrate is held in position on plate 61 by standoffs 6.

The carrier itself could be made of gold-plated aluminum and could be of any suitable size, for example of the order to 2 inches by 5 inches. The securing of substrates by means of standoffs assures intimate contact with the ground plane defined by the upper surface of carrier 61 and prevents the various substrates from moving.

The arrangement employed for mechanically retaining the various connectors disposed at the edge of the carrier is highly advantageous because of the ease and rapidity with which conductors can be replaced. Both types of housing according to the invention are highly advantageous because of their structural simplicity and the easewith which microstrip circuits can be assembled from individual wafers. This is particularly advantageous in the case of prototype circuit design.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations.

lclaim:

l. A flat carrier for at least one microstrip RF circuit element formed on a substrate, said carrier comprising: a polygonal carrier plate having the lower half of each of its edges cut away and the upper half of each of its edges provided with at least one slot for receiving a circuit connecting element which, when in place, extends below the upper half of such edge; holding means disposed in the cutaway portion of each edge of said plate for bearing against such connecting element; and attachment means extendingbetween each said holding means and its associated edgeof said plate for attaching said holding means to said plate and for clamping such connecting element between said holding means and said associated plate edge.

2. An arrangement as defined in claim 1 wherein said plate is rectangular and the cross section of each of said slots is in the form of a trapezoid whose small base is coextensive with the outer extremity of the upper half of its associated plate edge.

2. An arrangement as defined in claim-2 wherein said holding means are constituted by a plurality of strips each disposed along a respective edge of said plate and having a plurality of openings, said plate is provided, in the lower half of each of its edges, with threaded passages, and said attachment means are constituted by screws inserted through openings in each said strip and threadedly engaging said threaded passages in said plate. I 1

4. A microstrip RF circuit comprisin in combination:

a rectangular flat carrier having a at upper surface and provided with a plurality of holes formed in said surface and distributedat regular intervals thereacross in a square array, said carrier having connecting element receiving means along its edges;

a plurality of rectangular substrates each lying on said surface and each carrying a microstrip circuit element, the length of each edge of each substrate being equal to an integral multiple of the distance between adjacent holes;

holddown means inserted in said holes for holding said substrates in place; and

connecting elements mounted on said connecting element receiving means and connected to said circuit elements.

5. An arrangement as defined in claim 4 wherein the circuit element on each said substrate includes contact portions extending to the edges of said substrate for contacting corresponding contact portions of the circuit elements on adjacent substrates.

6. An arrangement as defined in claim 5 wherein each said substrate is square and has its corners cut out for the passage of said holddown means.

7. An arrangement as defined in claim 4 wherein said holes are threaded and said holddown means include screw elemerits threaded to mate with the threads in said holes.

8. A method for forming a microstrip RF circuit comprising:

providing a carrier having a flat support surface;

forming a square array of holes in said surface;

providing a plurality of substrates each carrying a RF circuit element and each having the form having the form of a standardized rectangle whose edge lengths are integral multiples of the distance between adjacent holes;

mounting such substrates on said surface and positioning each substrate so that the edges of adjacent substrates are in contact with one another and each corner of each substrate is adjacent a respective hole; and

engaging a holddown element in each hole which is adjacent a corner of a substrate to clamp such corner to said surface.

9. A method as defined in claim 8 comprising the further steps of forming connecting element-receiving means along the edges of said carrier and mounting connecting elements in said receiving means so that said elements contact substrate circuit elements.

10. A method as defined in claim 8 wherein said step of providing a plurality of substrates includes giving each RF circuit element contact portions extending to the edge of its respective substrate, and said step of mounting said substrates is carried out by disposing said substrates relative to one another so that contact portions on one said substrate make contact with corresponding contact portions on adjacent substrates.

11. A method as defined in claim 8 wherein each substrate is square and the length of each edge of the smallest standardized substrate is equal to the distance between adjacent holes. 

1. A flat carrier for at least one microstrip RF circuit element formed on a substrate, said carrier comprising: a polygonal carrier plate having the lower half of each of its edges cut away and the upper half of each of its edges provided with at least one slot for receiving a circuit connecting element which, when in place, extends below the upper half of such edge; holding means disposed in the cutaway portion of each edge of said plate for bearing against such connecting element; and attachment means extending between each said holding means and its associated edge of said plate for attaching said holding means to said plate and for clamping such connecting element between said holding means and said associated plate edge.
 2. An arrangement as defined in claim 1 wherein said plate is rectangular and the cross section of each of said slots is in the form of a trapezoid whose small base is coextensive with the outer extremity of the upper half of its associated plate edge.
 2. An arrangement as defined in claim 2 wherein said holding means are constituted by a plurality of strips each disposed along a respective edge of said plate and having a plurality of openings, said plate is provided, in the lower half of each of its edges, with threaded passages, and said attachment means are constituted by screws inserted through openings in each said strip and threadedly engaging said threaded passages in said plate.
 4. A microstrip RF circuit comprising in combination: a rectangular flat carrier having a flat upper surface and provided with a plurality of holes formed in said surface and distributed at regular intervals thereacross in a square array, said carrier having connecting element receiving means along its edges; a plurality of rectangular substrates each lying on said surface and each carrying a microstrip circuit element, the length of each edge of each substrate being equal to an integral multiple of the distance between adjacent holes; holddown means inserted in said holes for holding said substrates in place; and connecting elements mounted on said connecting element receiving means and connected to said circuit elements.
 5. An arrangement as defined in claim 4 wherein the circuit element on each said substrate includes contact portions extending to the edges of said substrate for contacting corresponding contact portions of the circuit elements on adjacent substrates.
 6. An arrangement as defined in claim 5 wherein each said substrate is square and has its corners cut out for the passage of said holddown means.
 7. An arrangement as defined in claim 4 wherein said holes are threaded and said holddown means include screw elements threaded to mate with the threads in said holes.
 8. A method for forming a microstrip RF circuit comprising: providing a carrier having a flat support surface; forming a square array of holes in said surface; providing a plurality of substrates each carrying a RF circuit element and each having the form having the form of a standardized rectangle whose edge lengths are integral multiples of the distance between adjacent holes; mounting such substrates on said surface and positioning each substrate so that the edges of adjacent substrates are in contact with one another and each corner of each substrate is adjacent a respective hole; and engaging a holddown element in each hole which is adjacent a corner of a substrate to clamp such corner to said surface.
 9. A method as defined in claim 8 comprising the further steps of forming connecting element-receiving means along the edges of said carrier and mounting connecting elements in said receiving means so that said elements contact substrate circuit elements.
 10. A method as defined in claim 8 wherein said step of providing a plurality of substrates includes giving each RF circuit element contAct portions extending to the edge of its respective substrate, and said step of mounting said substrates is carried out by disposing said substrates relative to one another so that contact portions on one said substrate make contact with corresponding contact portions on adjacent substrates.
 11. A method as defined in claim 8 wherein each substrate is square and the length of each edge of the smallest standardized substrate is equal to the distance between adjacent holes. 